What makes a number valid?
Each row, column, and 3×3 box must contain the digits 1 through 9 exactly once. Given digits cannot be changed. Pencil mode stores temporary candidates in an empty square without committing a final value.
Sudoku.
Nine rows, nine columns, nine boxes. Give every empty square its one correct number.
A little more about Sudoku.
How are puzzles chosen?
Choose Easy, Medium, or Hard, then press New puzzle. Each published puzzle has been checked for a single solution. Your entries and pencil notes are saved on this device.